#define _CRT_SECURE_NO_WARNINGS 1

class Solution {
public:
    int takeAttendance(vector<int>& records) {
        int left = 0, right = records.size() - 1;
        while (left < right)
        {
            int mid = left + (right - left + 1) / 2;
            if (mid < records[mid]) right = mid - 1;
            else left = mid;
        }
        if (records[left] > left) return left;
        return left + 1;
    }
};